New Zealand’s South Island – February 18th, 2009

The diverse geographical features of New Zealand’s South Island, including the Southern Alps and a number of lakes, are visible in this fine image.

The Southern Alps is a mountain range which runs along the western side of the South Island of New Zealand, forming a natural dividing range along the island’s entire length. Aoraki/Mount Cook is the highest point, at 3754 metres (12,283 feet).

In the close-up, the largest lakes visible from bottom to top are: Wanaka, Hawea, Ohau, Pukaki and Tekapo.

Lake Wanaka is located in the Otago region of New Zealand, in a glacial valley at an altitude of 300 metres. Covering an area of 192 km2, it is New Zealand’s fourth largest lake, and estimated to be more than 300 m deep.

About eight kilometers to the East, at an altitude of 348 metres, also located in the Otago Region, lies Lake Hawea. It covers an area of some 141 km² and is, at its deepest, 392 metres deep. In 1958 the lake was raised artificially by 20 metres to store more water for increased hydroelectric power generation. At its greatest extent, which is roughly along a north-south axis, the lake is 35 kilometres long.

It lies in a glacial valley parallel to that of nearby Lake Wanaka. At their closest point (a rocky ridge called The Neck), the lakes are only 1000 metres apart. The only flat land around the lake is at its southern end, surrounding its outflow into the Hawea River, a short tributary of the Clutha, which it joins near Albert Town.

Further east, Lake Ohau forms part of the traditional boundary between Otago and Canterbury regions. It is a glacial lake in the Mackenzie Basin. It is fed by the Hopkins and Dobson rivers, which have their headwaters in the Southern Alps, and has its outflow in the Ohau River, which itself feeds into the Waitaki River hydroelectric project.

Covering 60 km², Ohau is the smallest of three roughly parallel lakes running north-south along the northern edge of the Mackenzie Basin (the others are Lake Pukaki and Lake Tekapo). All three lakes were created by receding glaciers blocking their respective valleys with their terminal moraine (a moraine-dammed lake). The glacial feed to the lakes gives them a distinctive blue colour, created by glacial flour (extremely finely ground rock particles from the glaciers).

Lake Pukaki is an alpine lake along the northern edge of the Mackenzie Basin. It covers an area of 169 km², and the normal operating range lake level is 518.2 to 532 metres above sea level. The lake is fed at its northern end by the braided Tasman River, which has its source in the Tasman and Hooker Glaciers, close to Aoraki/Mount Cook.

The lake’s original outflow was at its southern end, into the Pukaki River. The lake is now, however, an upper part of the Waitaki hydroelectric scheme. As a result, the outflow has been dammed, and the water flows out through a canal linking it to a canal carrying water from Lake Ohau.

Finally, Lake Tekapo, the largest of the three Mackenzie Basin lakes, covers an area of 83 km², and is at an altitude of 700 metres above sea level. The lake is fed at its northern end by the braided Godley River, which has its source in the Southern Alps, to the north.